Britannica ImageQuest
Stockio
Pixabay (also Google Docs add-on)
Photos For Class
Unsplash (also Google Slides add-on)
PikWizard
Reshot
Morgue File
The Public Domain Review
Wikimedia Commons
Library of Congress
National Park Service Digital Image Archive
Flickr - The Commons
Pexels
Full Deck (also Google Docs add-on)
Every Stock Photo
The Noun Project (icons)
Videezy
Library of Congress and LOC National Screening Room
Public Domain Movies
Flickr (also how-to filter for videos)
Internet Archive
SoundzAbound
YouTube Audio Library
Dig CC Mixter
FreePlay Music
MusOpen
Bensound
Free Music Archive
Library of Congress and LOC Jukebox
Filmstro
Zapsplat
Sound Bible
Sound Gator